A. M. Toikka

Transport of Small Molecules through Polyphenylene Oxide Membranes Modified by Fullerene

Abstract Homogeneous membranes based on fullerene‐polyphenylene oxide compositions containing up to 2 wt% fullerene C60 were prepared. The effect of fullerene addition on PPO transport properties was studied in gas separation and pervaporation processes. Permeability coefficients of H2, O2, N2, CH4, and CO2 were measured; a correlation between gas transport properties and membrane free volume was established. Pervaporation properties were studied for the system with ethyl acetate synthesis reaction: quaternary system ethanol—acetic acid—water—ethyl acetate and some constituent binary and ternary mixtures. Pervaporation in binary systems, ethanol–water and ethyl acetate–water was considered with the use of the data on sorption capacities and interaction parameters. In pervaporation of a quaternary reacting mixture, the permeate containing essentially ethyl acetate was obtained. Results show that membranes with fullerene additives exhibit improved transport properties.

Polyamide Membranes Modified by Carbon Nanotubes: Application for Pervaporation

New polymer nanocomposites consist of poly(phenylene isophtalamide) (PA) modified by carbon nanotubes (CNT) were obtained by the solid state interaction method to prepare dense membranes. The investigation of the PA/CNT nanocomposites was made by Raman spectroscopy. The morphology of the dense membrane was analyzed by SEM. The transport properties of the dense polyamide membranes modified by 2 and 5 wt% CNT were studied in pervaporation of methanol/ methyl tert-butyl ether mixture. It was shown that the selectivity with respect to methanol and permeability were the highest for membranes containing 2 wt% CNT as compared to membranes of pure PA and containing 5 wt% CNT. To analyze transport properties the sorption tests and contact angle measurements were employed.

Conditions of thermodynamic equilibrium and stability as a basis for the practical calculation of vapour-liquid equilibria

Abstract Some main aspects of the thermodynamics of vapour–liquid equilibrium are considered together with a brief review of classical thermodynamic methods. The general thermodynamic–topological singularities of the structure of phase diagrams are discussed, as are the possible use of differential and integral thermodynamic relationships for the analysis and verification of phase equilibria. Special attention is given to results from the work of Russian researchers.

Vapor-liquid equilibria in systems with esterification reaction

The article presents a review of phase equilibrium data for four-component systems involving ester synthesis and hydrolysis reactions (acid-alcohol-ester-water) systems. A brief characteristic of the experimental and calculated data is given.

Splitting of the liquid solution and the compositions of liquid phases in the water-n-propanol-n-propyl acetate system at 293.15, 303.15, and 313.15 K

New experimental data on solubility and liquid-liquid phase equilibrium in a water-n-propanol-n-propyl acetate system under polythermal conditions are presented. The results of modeling the liquid-liquid equilibrium using the UNIFAC model are given.

Solubility in the system constituted by acetic acid, n-propanol, water, and n-propyl acetate

Experimental data on the solubility in the system constituted by acetic acid, n-propanol, water, and n-propyl acetate at 313.15 K are presented. The position of the critical curve for the liquid-liquid equilibrium, including that of the critical points on the chemical equilibrium surface, is discussed.

Solubility and critical phenomena in reactive liquid–liquid systems

The goal of this work is to consider solubility phenomena in reactive fluid mixtures with liquid-phase splitting. One of the main tasks is to analyze peculiarities of liquid–liquid (LL) systems with equilibrium and nonequilibrium chemical reaction. The special aim is to consider the critical states in these systems. The reactive liquid–liquid equilibrium (LLE) is treated on the base of phase rule. The topology of diagrams of reactive LLE is discussed for some types of binary and ternary systems. Examples are presented of a possible transformation of phase diagrams caused by the shifting of chemical equilibrium and by changes in the shape of the binodal. The transformations resulting in the reactive critical phase formation are considered. Quaternary mixtures are also discussed with the use of experimental data on the solubility in the system with n-propyl acetate synthesis reaction. The mutual crossing of the chemical equilibrium surface and binodal in the composition tetrahedron leads to the origin of the area of simultaneous chemical and LLE with two critical points (reactive critical phases). The shape of the curve of simultaneous chemical and phase equilibrium is also presented in the square of transformed composition variables.

Experimental study of chemical equilibrium and vapor-liquid equilibrium calculation for chemical-equilibrium states of the n-propanol-acetic acid-n-propyl acetate-water system

Chemical equilibrium data for the n-propanol-acetic acid-n-propyl acetate-water system at 303.15 K are presented. The results of UNIFAC-based modeling of the vapor-liquid equilibrium in the system at 303.15 and 313.15 K are reported.

Spread Films of Synthetic Polyelectrolyte-Surfactant Complexes : Dilational Viscoelasticity and Effect on Water Evaporation

Data are presented on the dynamic surface properties of films formed from sodium polystyrenesulfonate-dodecyltrimethylammonium bromide (PSS-DTAB) and poly(diallyldimethylammonium chloride)-sodium dodecyl sulfate (PDADMAC-SDS) complexes by the spreading of the above substances onto a water surface from their concentrated solutions. These films are shown to be stable up to surface pressures of 20 mN/m (PSS-DTAB) and 37 mN/m (PDADMAC-SDS). In the latter case, when the limiting surface pressure is reached, microaggregates are formed in the surface layer along with the film dissolution. The surface films in question markedly decelerate water evaporation, and this phenomenon cannot be explained in terms of the classical Goddard model of the structure of films prepared from polyelectrolyte-surfactant complexes and, at the same time, is in good agreement with a recently proposed model that takes into account hydrophobic interactions.

Structure and Transport Properties of Fullerene–Polyamide Membranes

Poly‐(phenylene‐iso‐phtalamide) was modified by fullerene C60 and other nanocarbon additives such as nanotubes and soot. These compositions were used for ultrafiltration membranes formation. To estimate the fullerene effect on polyamide properties, intrinsic viscosity and density of compositions containing up to 10 wt% C60 were measured. In addition, overall porosity of asymmetric membranes and contact angle of water on membranes surface were determined. Membranes structure rigidity and resistance to different solvents were estimated by filtration of liquids with different viscosities through membranes modified by 5 wt% fullerene, soot or nanotubes. All nanocomposite membranes were tested in dynamic (ultrafiltration) and static sorption experiments with solution of proteins mixture with different molecular weights to study proteins sorption. Membranes modified by fullerene and nanotubes demonstrated the best values of flux reduced recovery after contact with proteins solution.